Apparatus and devices of the type with which the invention is concerned are described in U.S. Pat. Nos. 5,271,297 and 5,330,159 both assigned to the same assignee as this application. A tensioning or clamping device is also described in GB 1444606 in which hydraulic piston and cylinder units supported on a carrier ring subject couplings on the screw-threaded members to tensile force. In this arrangement, each of the couplings and the heads of the screw-threaded members have inter-engageable jaws and grooves. The nuts on the screw-threaded members lie beneath the couplings relative to the vessel and are rotated with a special drive having a pinion wheel which can pass through apertures in the carrier ring to mesh with teeth on the nuts. When one of the nuts is connected the drive and is to be rotated an associated piston and cylinder unit is charged with pressure fluid to lift the coupling and brace the screw-threaded member so the nut can be rotated on the screw-threaded member.
In U.S. Pat. No. 5,330,159 to transfer the high forces of hydraulic units to the screw-threaded members in order to tension and stretch them, sleeves or gripper nuts are screwed onto the screw-threaded members as extensions from above the upper end of the members. Screwing and unscrewing the powerful gripper nuts onto and off the ends of the screw-threaded members requires considerable additional energy and has to be carried out by means of special rotary actuators with geared motors.
However, it its also known from DE 2146608 that instead of using hollow gripper nuts solid auxiliary extension elements can be selectively connected to the screw-threaded members by means of external coupling mechanisms, which each have two semi-shell shaped coupling segments screwed onto the ends of the screw-threaded member and the auxiliary extension. The segments are displaced by means of a coupling lock operated by an activating piston and cylinder to lock these elements together positively. Although these devices can be used if the screw-threaded member protrudes with its end over the unscrewed cover-fastening nut only relatively slightly, the coupling mechanism with its coupling lock still takes up a relatively large amount of space. This creates considerable problems especially when the screw-clamping device is used for pressurised reactor vessels as in this case the screw-threaded members have to be arranged at short distances from one another and there is therefore only limited space available for setting up the clamping devices.
The main objective of the invention is to improve the clamping device of the above type in particular with respect to its coupling mechanism, so that very high tensile and clamping forces can also be reliably transferred yet the device is able to have comparatively small dimensions and can also operate with small adjustments on closing and opening.